RNA Trades Bit Part for Starring Role in the Cell - New York Times
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9/27/06 11:05 AM
January 21, 2003
RNA Trades Bit Part for Starring Role in the Cell
By ANDREW POLLACK
In the family of genetic material, RNA has long been the poor cousin of DNA. DNA makes up the
genes, the master instructions of life, while RNA merely conveys those instructions to other parts of the
But surprising new discoveries are showing that cells contain an army of RNA snippets that do much
more than act as DNA's messenger. The discoveries are helping to refine the prevailing theories of
genetics -- or even upend them.
''It's like discovering the neutrino or something,'' said Dr. Gary Ruvkun, a professor of genetics at
Harvard Medical School. ''These things were all around us for many years,'' and no one was aware of
them. ''Now we're discovering they are all over the place,'' he added. ''Genomes are full of them.''
The discoveries are having practical applications. Scientists have found that tiny snippets of RNA with
two strands instead of the usual one can be used to shut off specific genes. The technique, known as
RNA interference, is being widely used to discover the functions of genes by turning them off and
seeing what happens to the plant or animal.
In a paper published in Nature on Thursday, Dr. Ruvkun and his colleagues at Harvard and
Massachusetts General Hospital used RNA interference to turn off almost all of a worm's genes, one at a
time, to discover those linked to obesity. Doctors hope that RNA interference will one day be used for
medicine, inactivating genes, say, in tumors or viruses.
''This is a gift from heaven,'' said Dr. Phillip A. Sharp, a Nobel laureate and a professor of biology at the
Massachusetts Institute of Technology. He is also a founder of Alnylam Pharmaceuticals, one of several
companies started to exploit RNA interference. Many other companies are trying to develop drugs based
on other aspects of RNA.
Dr. Stuart Peltz, chief executive of PTC Therapeutics in South Plainfield, N.J., said RNA had become
''sort of a huge discovery zone.'' PTC is developing drugs that influence the way RNA works.
Scientists have recently reported that Prader-Willi and Fragile X syndromes, each leading to mental
retardation, and chronic lymphocytic leukemia may be linked to RNA defects. Biologists studying other
species are also looking to RNA for answers to unsolved mysteries.
''Everybody wants to look in their favorite organism or favorite system and see if there's an RNA lurking
there,'' said Dr. Susan Gottesman, chief of biochemical genetics at the National Cancer Institute, who
studies E. coli bacteria. ''A lot of the regulatory puzzles in E. coli are explained by small RNA's we didn't
think were there.''
RNA and DNA are strings of chemical units called bases that embody the genetic code. The bases are
represented by the letters A, C, G and either T in DNA or U in RNA. The C base always binds to G. A